Deep Mixing Research Articles

Effect of elevated temperature on geotechnical properties of soils – A review

Land used for construction purposes should have large bearing capability and less squeezability. Soft soils such as clayey soil have low bearing capacity and high compressibility which must be converted or treated before the construction process to meet the requirements. The presence of oil and gas pipe lines, buried high voltage cables, fire accidents, storage of high-level waste could limit the use of conventional methods such as deep cement mixing. Hence, alternate methods are required, heat treatment has been considered to be the efficient technique, if the need of enhancement in characteristics are required. This paper discusses the literature available on thermal treatment. The effect of temperature on various properties of soil like Atterberg limits, free swell, porewater pressure, swelling, shear strength, stress strain behavior of soil and mineralogy is included in this paper. This review paper summarizes the effectiveness of thermal treatment on soft soil.

Physical and Mechanical Characterization of Deep Soil Mixing (Dsm) Materials: Laboratory vs Construction Site

Physical and Mechanical Characterization of Deep Soil Mixing (Dsm) Materials: Laboratory vs Construction Site

Enhancement of Lithium in Red Clump Stars by Neutrino Magnetic Moments

A recent spectroscopic survey has shown that the lithium abundances in low-mass red-clump stars are higher than theoretical prediction. Motivated by their finding, we implemented effects of additional energy losses induced by neutrino magnetic moments on stellar evolution models. It is found that the lithium abundances in red giants increase because the finite magnetic moments of neutrinos enhance the efficiency of deep mixing and 7Be is conveyed from the hydrogen burning shell to the convective envelope. The results motivate further studies on the effects of non-standard energy losses on the surface compositions of low-mass red giants and red-clump stars.

Investigation of the Relationship Between Elasticity Modulus and Unconfined Compressive Strength in Soils Improved by Deep Mixing Method

Derin karıştırma yöntemi, zayıf zeminlerin özelliklerinin çimentolu bir bağlayıcı ile karıştırılarak mekanik olarak yerinde iyileştirilmesi ve zeminde kolonlar oluşturulması şeklinde tanımlanan bir zemin iyileştirme yöntemidir. Bu yöntemde bağlayıcı malzeme olarak daha çok çimento ve kireç kullanılmaktadır. Bu yöntem ile iyileştirilen zeminlerin özellikleri; tabii zeminin ve bağlayıcıların özelliklerine, katkı miktarına ve kür süresine bağlıdır. Derin karıştırma ile iyileştirme yapılan tasarımlarda kalite kontrol deneylerinde genellikle serbest basınç mukavemet değerleri ölçülmekte ve deformasyonların tayini için gereken modül değerlerine korelasyonlar yardımı ile geçilmektedir. Bu çalışma kapsamında öncelikle dünya genelinde kabul görmüş olan standartlar anlatılmış ve bu yönteme dair ülkemizde oluşturulabilecek bir şartname için bilgiler toplanmış, tavsiyeler verilmiştir. Çalışma kapsamında literatürde mevcut olan çalışmalar incelenmiş ve derin karıştırma ile elde edilen malzemelerin mukavemet-modül değerleri bir veri tabanına işlenmiştir. Bu kapsamda 12 ayrı çalışmadan toplamda 545 adet veri toplanmıştır. Oluşturulan veri tabanı zemin tipi, katkı tipi ve miktarı, kür süresi, serbest basınç mukavemeti, Elasitisite modülü ve karıştırma metodu bilgilerini içermektedir. Veri tabanı kullanılarak yeni korelasyonlar aranmış ve mevcut olanlarla karşılaştırılmıştır. Elde edilen korelasyonların ülkemizde son yıllarda çok yoğun kullanım alanı bulmakta olan derin karıştırma yöntemi için faydalı olacağı düşünülmektedir.

Improving mechanical properties and shrinkage cracking characteristics of soft clay in deep soil mixing

Deep soil mixing is a ground improvement method that enhances the characteristics of soft soils by mechanically mixing the soil with cementitious binders such as cement and fly ash (FA). The objective of this paper is to investigation the post-treatment mechanical properties and shrinkage cracking characteristics of soft Bangkok clays treated with ordinary Portland cement (OPC) and FA. Unconfined compressive strength, modulus of elasticity, and shrinkage cracking after 7 and 28 days of mixture curing were measured. The effects of wet/dry cycling on the durability of mixtures were examined. Microstructures of treated soft clays were examined using scanning electron microscopy with energy dispersive x-ray analysis (SEM/EDX) techniques. Test results showed that strength and stiffness improvements of stabilised soft clays increased with OPC content but decreased with FA content, while the extent of sample shrinkage decreased with increasing FA content. Based on these results, we propose the preliminary guideline of applying 15% replacement of OPC with FA to obtain the optimal mixture ratios that allows FA to act as a shrinkage-reducing agent for deep soil mixing purposes. By adding OPC and 15% FA at a binder-per-water ratio (B/wc) of 0.4, the stabilised soft clay satisfied both strength and shrinkage cracking criteria for deep soil mixing purposes. SEM/EDX analyses further supported these experiment results. In addition, correlations between the mechanical properties and the chemical compositions of stabilised soft clay were derived and presented.

Life Cycle Sustainability Assessment of Geotechnical Ground Improvement Methods

A life-cycle sustainability assessment evaluated and compared the impacts of five ground improvement methods commonly implemented to mitigate liquefaction: compaction grouting, deep dynamic compaction, deep soil mixing, vibro compaction, and vibro replacement (i.e., stone columns). Using typical scopes of work provided by geotechnical contractors who specialize in ground improvement, this study developed sustainability benchmarks for the life-cycle impacts and costs of each method, quantified the consequences of the risk and uncertainty inherent in ground improvement projects, and examined impacts to land and soil resources that occur throughout the life cycle. Results showed that deep soil mixing and compaction grouting are the most impactful and costly methods due to the use of portland cement, an energy- and emissions-intensive material. Vibratory methods and deep dynamic compaction are more sustainable, despite the fact that their impacts and costs are more variable and uncertain. Although many factors influence ground improvement design selection (e.g., safety, performance criteria, feasibility, and cost), the results of this study may help inform decision making to realize more sustainable infrastructure.

Settlement mechanism and improvement of thick silty sand layer overlying mud foundation

Many highways have been built on the eastern coast of China in the past decades. Recently, some engineering problems have emerged after long-term operation. Due to the different properties between the underlying soil and bridge pile foundations, the problem of bumping at the bridge head is inevitable. To study the potential causes and provide insight for future improvement, the settlement of typical highways in the Hangzhou Bay area, which had been open to traffic for more than 10 years, was investigated. After an analytical calculation with the verification of the numerical method and field data, it was indicated that long-term deformation was mainly caused by the poor properties of the lower of the two layers that make up the underlying soil. The trend of the variation of the lower layer keeps increasing at a slow rate during the construction period, resulting in sustained and rapid changes during the following years. Different kinds of ground improvement such as lightweight materials and soil–cement columns generated by deep mixing or jet grouting methods are discussed. The improvement of the lower layer will be more effective. With the analytical method, it is convenient and efficient to calculate and analyse the settlement at different periods, which is significant for design.

Low temperature sensitivity of picophytoplankton P : B ratios and growth rates across a natural 10°C temperature gradient in the oligotrophic Indian Ocean

AbstractWe investigated temperature sensitivities of picophytoplankton growth along a natural 10°C (18–28°C) temperature gradient in the eastern Indian Ocean characterized by deep mixing and consistently low dissolved nitrogen. Population biomass (B), cell carbon, and chlorophyll were measured by flow cytometry. Instantaneous growth (μ) and production (P) were calculated from dilution incubations at four light levels. Contrary to most empirical and theoretical predictions, Prochlorococcus, the biomass dominant, showed insignificant temperature sensitivity, with nominal Q10 values of 1.06 and 1.18 for P : B and μ, respectively, and activation energies (Ea) of 0.05 and 0.12 eV. Q10 and Ea values for Synechococcus (1.36–1.42 and 0.23–0.27 eV) were also below prediction, and picoeukaryotes showed high variability, including negative rates suggesting lytic cycles, at high temperature. We emphasize the importance of using adapted communities in natural environmental gradients to test climate predictions and hypothesize that mortality defenses are a significant selection criterion in balanced oligotrophic systems.

Seasonal mixed layer depth shapes phytoplankton physiology, viral production, and accumulation in the North Atlantic

Seasonal shifts in phytoplankton accumulation and loss largely follow changes in mixed layer depth, but the impact of mixed layer depth on cell physiology remains unexplored. Here, we investigate the physiological state of phytoplankton populations associated with distinct bloom phases and mixing regimes in the North Atlantic. Stratification and deep mixing alter community physiology and viral production, effectively shaping accumulation rates. Communities in relatively deep, early-spring mixed layers are characterized by low levels of stress and high accumulation rates, while those in the recently shallowed mixed layers in late-spring have high levels of oxidative stress. Prolonged stratification into early autumn manifests in negative accumulation rates, along with pronounced signatures of compromised membranes, death-related protease activity, virus production, nutrient drawdown, and lipid markers indicative of nutrient stress. Positive accumulation renews during mixed layer deepening with transition into winter, concomitant with enhanced nutrient supply and lessened viral pressure.

Composite contiguous pile wall and deep mixing column wall as a dam –Design, construction and performance

This paper presents a case study on the application of a composite contiguous-pile wall and deep mixing (DM) column wall as a dam to develop a luxury lake in Lake Legend Chaengwatthana project, Bangkok, Thailand. This dam was constructed in a deep rainwater pond without providing the water removal, which could save on both time and cost construction. The design and construction method were challenging because the dam was located on the soft and thick Bangkok clay. The dam was designed by finite element analyses (FEA) using PLAXIS software. The 2 rows of contiguous-pile walls were first executed and then filled with soft clay. The DM columns were used to strengthen the clay backfill. The FEA results at normal and rain-shortage stages confirm the stability of the dam with accepted deformation. With insignificant water seepage over time, the dam acted as the waterproof barrier. The field performance of the dam during construction and at service state over 276 days were recorded and compared with FEA results. The numerical simulation slightly over-predicted the lateral displacement. The difference in the displacement between the measured and simulated data reduced significantly with depth. The rate of consolidation by the numerical simulation results were slightly slower than that by the field measurement. The outcome of this research will be fundamental to develop a design guideline of ground improvement in soft Bangkok clay and other similar soft clay deposits especially in Southeast Asian countries.

Surface Salinity Under Transitioning Ice Cover in the Canada Basin: Climate Model Biases Linked to Vertical Distribution of Fresh Water

AbstractThe Canada Basin has exhibited a significant trend toward a fresher surface layer and thus a more stratified upper‐ocean over the past three decades. State‐of‐the‐art ice‐ocean models, by contrast, tend to simulate a surface layer that is saltier and less stratified than observed. Here, we examine decadal changes to seasonal processes that may contribute to this wide‐reaching model bias using climate model simulations from the Community Earth System Model and below‐ice observations from the Arctic Ice Dynamics Joint Experiment in 1975 and Ice Tethered Profilers in 2006–2012. In contrast to the observations, the models simulate salinity profiles that show relatively little variation between 1975 and 2012. We demonstrate that this bias can be mainly attributed to unrealistically deep vertical mixing in the model, creating a surface layer that is saltier than observed. The results provide insight for climate model improvement with broad implications for Arctic sea ice and ecosystem dynamics.

Selection of Optimized Binders for Dechlorination of Trichloroethylene-Contaminated Sites by Jet Grouting and Deep Soil Mixing

AbstractThe remediation of sites contaminated with chlorinated hydrocarbons (CHCs) poses a challenge, especially in built up areas. Nanoscale zero-valent iron (nZVI) can reduce CHCs to nontoxic com...

Performance of Using Waste Marble Dust for the Improvement of Loose Sand in Deep Soil Mixing

Performance of Using Waste Marble Dust for the Improvement of Loose Sand in Deep Soil Mixing

Recent Development and Future Perspectives of Quality Control and Assurance for the Deep Mixing Method

The deep mixing method (DMM), an in situ soil stabilization technique, was developed in Japan and Nordic countries in the 1970s and has gained increased popularity in many countries. The quality of stabilized soil depends upon many factors, including its type and condition, the type and amount of binder, and the production process. Quality control and quality assurance (QC/QA) practices focus on stabilized soil, and comprises laboratory mix tests, field trial tests, monitoring and controlling construction parameters, and verification. QC/QA is one of the major concerns for clients and engineers who have less experience with the relevant technologies. In this manuscript, the importance of QC/QA-related activities along the workflow of deep mixing projects is emphasized based on the Japanese experience/results with mechanical mixing technology by vertical shaft mixing tools with horizontal rotating circular mixing blade. The current and recent developments of QC/QA are also presented.

Seismic response of pile groups improved with deep cement mixing columns in liquefiable sand: shaking table tests

A series of shaking table model tests were performed to examine the effects of deep cement mixing (DCM) columns with different reinforcement depths on the seismic behavior of a pile group in liquefiable sand. Due to the DCM column reinforcement, the fundamental natural frequency of the model ground increases noticeably. The excess pore pressure of soils reduces with the increase of reinforcement depths of the DCM columns. Before liquefaction, the acceleration response of soils in the improved cases is obviously lower than that in the unimproved case, but the acceleration attenuation is greater after liquefaction in the unimproved case. Moreover, the lateral displacement of the superstructure, the settlement of the raft, and the bending moment of the piles in the improved cases are significantly reduced compared with those in the unimproved case, and the reduction ratios rise with the increase of reinforcement depth of the DCM columns. However, reinforcement by the DCM columns may result in the variation of the location of the maximum moment that occurs in the pile.

Estimation of Allowable Bearing Capacity and Settlement of Deep Cement Mixing Method for Reinforcing the Greenhouse Foundation on Reclaimed Land

Estimation of Allowable Bearing Capacity and Settlement of Deep Cement Mixing Method for Reinforcing the Greenhouse Foundation on Reclaimed Land

Visual Performance Evaluation of Relative Agitating Type of Deep Mixing Method by Computer Simulation and Agitation Model Experiment

Visual Performance Evaluation of Relative Agitating Type of Deep Mixing Method by Computer Simulation and Agitation Model Experiment

Winter dissolved and particulate zinc in the Indian Sector of the Southern Ocean: Distribution and relation to major nutrients (GEOTRACES GIpr07 transect)

First winter measurements of dissolved zinc (dZn) and particulate zinc (pZn) are presented from seven stations, between 41 and 58°S, occupied in July 2017 along the 30°E longitude in the Indian Sector of the Southern Ocean. This unique spatial and seasonal dataset provided the opportunity to investigate Zn biogeochemical cycling in a region which is extremely data scarce and during a period when conditions are unfavourable for phytoplankton growth. Surface comparisons of our winter dZn and pZn to previous measurements during spring and summer revealed that Zn seasonality is most pronounced at the higher latitudes where higher dZn (and higher ratios of dZn to phosphate; dZn:PO4) and lower pZn in winter reflect decreased biological uptake and preferential dZn resupply (relative to PO4) to surface waters through deep winter mixing. The composition of pZn was majorly biogenic however localised lithogenic inputs were attributed to potential hydrothermal activity and transport of continental sediment via Agulhas waters. Calculated vertical attenuation factors (b values) for pZn (0.31) and phosphorus (P; 0.41) suggest that Zn has a longer remineralisation length scale than P, providing a mechanism as to why dZn appears to be remineralised deeper in the water column than PO4. Ratios of pZn to P (pZn:P) in surface waters increased with latitude from 1.12 to 8.28 mmol mol−1 due to increased dZn availability and the dominance of diatoms (with high cellular Zn quotas) in the high latitude Antarctic Zone (AAZ). Interestingly, the high surface pZn:P ratios in the AAZ did not change significantly with depth (in contrast to the northern stations where pZn:P increased with depth) suggesting the export of diatom cells below the winter mixed layer where remineralisation and rigorous mixing may resolve the linear dZn to silicic acid (dZn:Si(OH)4) correlation (dZn (nmol kg−1) = 0.064 Si(OH)4 (μmol kg−1) + 0.690; r2 = 0.93; n = 120) despite these elements being located in separate components of the diatom cell. Additionally, elevated concentrations of dZn and Si(OH)4 below 3000 m in the AAZ may reflect nutrient accumulation in bottom waters where northward flow is inhibited by the Indian mid-Ocean ridge.

A new framework for quantifying the structure of undisturbed and artificially cemented alluvium

Silty alluvial soils are highly compressible. Deep soil mixing is being increasingly used for remediating such ground conditions, which produces artificially cemented soil columns that gain strength with curing. This study investigated the one-dimensional compression and shear stiffness degradation behaviour of an alluvium in its reconstituted, undisturbed and artificially cemented states. The binder used to stabilise the soil was a low-carbon alkali-activated blast-furnace slag. Oedometer and triaxial data indicated that the nature of the soil structure evolved from being chiefly meta-stable when undisturbed to dominantly stable in its cemented state after 28 days of curing. A new framework has been presented to quantify continuous changes in structure within the alluvium during one-dimensional compression in its undisturbed and cemented states, with respect to its intrinsic properties. This better captured structure degradation during earlier stages of compression compared with previous frameworks and provided insights into defining the limits of meta-stable and stable components of structure within materials of higher strength. A new formulation has been developed for predicting shear stiffness degradation of samples with strain under triaxial conditions. This showed efficiency and good performance in modelling experimental data and was successfully used to quantify initial structure and degradation of structure within the undisturbed and cemented alluvium.

Planktic foraminiferal changes in the western Mediterranean Anthropocene

The increase in anthropogenic induced warming over the last two centuries is impacting marine environment. Planktic foraminifera are a globally distributed calcifying marine zooplankton responding sensitively to changes in sea surface temperatures and interacting with the food web structure. Here, we study two high resolution multicore records from two western Mediterranean Sea regions (Alboran and Balearic basins), areas highly affected by both natural climate change and anthropogenic warming. Cores cover the time interval from the Medieval Climate Anomaly to present. Reconstructed sea surface temperatures are in good agreement with other results, tracing temperature changes through the Common Era (CE) and show a clear warming emergence at about 1850 CE. Both cores show opposite abundance fluctuations of planktic foraminiferal species ( Globigerina bulloides , Globorotalia inflata and Globorotalia truncatulinoides), a common group of marine calcifying zooplankton. The relative abundance changes of Globorotalia truncatulinoides plus Globorotalia inflata describe the intensity of deep winter mixing in the Balearic basin. In the Alboran Sea, Globigerina bulloides and Globorotalia inflata instead respond to local upwelling dynamics. In the pre-industrial era, changes in planktic foraminiferal productivity and species composition can be explained mainly by the natural variability of the North Atlantic Oscillation, and, to a lesser extent, by the Atlantic Multidecadal Oscillation. In the industrial era, starting from about 1800 CE, this variability is affected by anthropogenic surface warming, leading to enhanced vertical stratification of the upper water column, and resulting in a decrease of surface productivity at both sites. We found that natural planktic foraminiferal population dynamics in the western Mediterranean is already altered by enhanced anthropogenic impact in the industrial era, suggesting that in this region natural cycles are being overprinted by human influences. • Western Mediterranean planktic foraminifera and sea surface temperature records. • Planktic foraminiferal changes explained by natural variability in pre-industrial times. • Anthropogenic warming depletes marine surface production.